[0001] The present invention relates to a pneumatic radial tire, more particularly to a pneumatic radial tire having driving stability and load durability applicable to a high performance passenger vehicle.
[0002] Conventionally, as a radial tire for a high performance passenger vehicle, for example, a pneumatic radial tire has been known in which the carcass layers are a two-layer structure as shown by FIG. 2. According to the tire shown by FIG. 2, two carcass layers 28 and 30 are arranged to reach a bead portion 26 from a tread portion 22 via a side portion 24. Whereas both end portions of the carcass layer 28 on an inner side are respectively folded back from an inner side of the tire to an outer side of a tire to wrap the bead fillers 34 around left and right bead cores 32, both end portions of the carcass layer 30 on an outer side are turned down to vicinities of bead toes via inner diameter sides of the bead cores 32 to cover outer sides of fold back portions 28b of the carcass layer 28. Further, reinforcement layers 36 comprising steel cords are arranged between the carcass layer 30 on the outer side and fold back portions 28b of the carcass layer 28 on the inner side. Further, two belt layers 38 are arranged on an outer side of the carcass layer 30 on the outer side at the tread portion 22.
[0003] In viewing passenger vehicles on sale in recent years, a vehicle having a power output of 280 horsepower and a mass of 1.5 tons has become more common than a vehicle having a displacement of 2000 cc. In the case of the conventional tire structure shown by FIG. 2, it is difficult to ensure driving stability and load durability for such a vehicle. However, when widths of reinforcement layers of a tire are uselessly widened or a number of the layers is increased, a problem can occur in which not only is there an increase in the tire mass but also the load durability deteriorates.